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Author Topic: 8V71 Won't Start  (Read 4691 times)
pabusnut
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P8M4905A-333 former MK&O lines #731




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« on: March 04, 2011, 05:08:52 PM »

Haven't started the 8V71 for a couple of months, as it has been too cold to do anything here in PA.  Was going to take it to get brakes adjusted and an air leak fixed tomorrow, but.....it won't start!

It did start but ran only long enough to suck some of the fuel out of the new spin on filters. 

A little history is in order:  I was having trouble with the system losing prime, but figured it was my old canister type filters, so I switched over to spin on filters with new bases back in October.  I made one run to a campground about 45 minutes away, and all was good.

Today, when I start the engine, it fires right up, but then gets starved for fuel.  I pull the primary filter, and yes, it is only half full, so I fill it up right to the top.  I check the secondary, and it is down a little too, so I fill it up also.  I get back on the starter and it spins over, but won't fire.  Previous times when I had this problem, it would start after the filters were filled.  I kept trying till I noticed the starter slowing down--which means I knocked down the batteries a bit.  The charger is now on the batteries, hoping I can get them up to par so I can try again in the morning.

First I am confused about how it would lose prime, and second why it won't start after filling the filters?

Do I need to use a funnel and  fill through one of the ports on the filter base until fuel gets back to the tank?  I My fuel gauge tells me that nobody "borrowed" a significant amount of fuel so I don't think fuel is a problem.

Any help is greatly appreciated!

Steve Toomey
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Steve Toomey
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TedsBUSted
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« Reply #1 on: March 04, 2011, 06:01:04 PM »

. . .A little history is in order:  I was having trouble with the system losing prime, but figured it was my old canister type filters, so I switched over to spin on filters with new bases back in October.  I made one run to a campground about 45 minutes away, and all was good.


. . .First I am confused about how it would lose prime, and second why it won't start after filling the filters?

Hello PA,
Given the described history I'd bet on a bad check valve or an air leak on the suction side of the system.
Pull the supply line from the primary filter's out port and see if backward flow to the tank is checked, or blocked. Easy, just a little pressure, don't blast it with shop air.

Same pressure testing technique applied before the check valve will possibly hopefully make any air leak noticeable. The supply pump's shaft seal is another potential leak source.

Not immediately starting after simply filling the filters is because the supply circuit to the injectors is still dry.

I'll mention that it takes a while for fuel to soak into filter elements to completely fill a filter for priming. A utility hand-pump that will pull a vacuum makes a very effective system primer. Connection point depends on what's accessible; sometimes a gauge port on top of the filter housing; sometimes the return line, but then you're pulling through the fuel pump, anyway, it still works.

good luck
« Last Edit: March 04, 2011, 06:07:14 PM by TedsBUSted » Logged

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rampeyboy
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« Reply #2 on: March 04, 2011, 06:37:30 PM »

I had a heck of a time starting mine at first. My filter was full, but the thing obviously was getting no fuel. The line before and after the filter was dry, but the filter full. Strange. Anyway, I finally broke down and put an electric inline pump on the thing. I ran it a few minutes until I had fuel coming out of the line at the filter, reconnected that line, and then ran the electric pump more. I thought that should do it. Nope. Ran the electric pump a while longer. Tried again and finally it took off and ran. Has been ok since. I left the inline electric pump in place in case it ever happens again!

Boyce
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Boyce Rampey
Columbia, SC
Scenicruiser 227
gus
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« Reply #3 on: March 04, 2011, 07:46:48 PM »

I agree with Ted, my check valve failed and the exact same thing happened until I repaired it.

I'm going to install and electric pump just like Boyce in case this ever happens again, probably at a very inconvenient time!
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pabusnut
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P8M4905A-333 former MK&O lines #731




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« Reply #4 on: March 04, 2011, 08:02:06 PM »

Thanks guys!

I guess I will have to find that check valve and fix replace it just to get it to the shop.

Does anybody know where I can get a small 24VDC inline pump?  I just noticed yesterday that my 'New to Me-2006 Jeep Liberty CRD has the little "thumb pump thingy" right on the side of the fuel filter housing.  Novel Idea. 

I wish I could find  one of themanual pumps that were rumored to be on early Macks.

Steve Toomey
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Steve Toomey
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« Reply #5 on: March 04, 2011, 08:11:24 PM »

Thinking out of the box but some common sense. Why a 24 volt pump? Probably something you may need for 20 seconds a year. Plumb in a common 12 volt pump and jump it with your house batteries. 
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pabusnut
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P8M4905A-333 former MK&O lines #731




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« Reply #6 on: March 04, 2011, 08:44:58 PM »

I guess I didn't think about a 12V pump?!  I could basically use a "long extension cord" to get to the batteries in a pinch, or use the toad battery.

PAbusnut
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Steve Toomey
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« Reply #7 on: March 04, 2011, 08:51:46 PM »

My generator has a electric fuel pump. I carry a spare for it got it at Napa. I have never had a fuel problem yet. But that is probably why, I carry a spare.
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papatony
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« Reply #8 on: March 05, 2011, 03:46:45 AM »

     You have  12 volts at your starier or gen.  A 5 ft. cord and a couple of clips and you are in buss.
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thomasinnv
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« Reply #9 on: March 05, 2011, 06:59:18 AM »

     You have  12 volts at your starier or gen.  A 5 ft. cord and a couple of clips and you are in buss.

I would guess he's probably got 24v if he was asking about 24v pumps.
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luvrbus
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« Reply #10 on: March 05, 2011, 07:15:11 AM »

Plenty of other thing will cause a loss of prime besides the check valve I never had a check valve on my Eagle installed  one 65 bucks from DD it still lost prime chased in down it was a hose removed the check valve it's still doing ok as far as I know.
Invest you money in a inline flo/through pump for 70 bucks

good luck
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gus
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« Reply #11 on: March 05, 2011, 05:08:38 PM »

Are all electric pumps flo-thru, seems to me they should be but is a small auto electric pump large enough for a bus flo-thru??
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PD4107-152
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Greg Smith
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« Reply #12 on: March 06, 2011, 12:50:58 PM »

Yes. I've been running my 8V71 on a NAPA 12v fuel pump for 3years and no problems.
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gus
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« Reply #13 on: March 07, 2011, 03:42:31 PM »

Greg, thanks. Do you have it inline or is it set up in parallel?
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PD4107-152
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rampeyboy
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1954 Scenicruiser PD4501-227




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« Reply #14 on: March 07, 2011, 06:27:34 PM »

Guys, I had this one,

http://www.summitracing.com/parts/ATX-E8012S/

and put it inline to prime my 8V71. It worked fine for that purpose. It is still in place, but not hooked up. The mechanical pump seems to pull through it just fine, but I have only let the engine run at home..not road worthy yet....

Boyce
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Boyce Rampey
Columbia, SC
Scenicruiser 227
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